JPWO2016148127A1 - User apparatus, base station, and communication method - Google Patents

Abstract

A user apparatus that communicates with the base station in a wireless communication system comprising a base station and a user apparatus, wherein the first receiving means receives a plurality of first reference signals transmitted from the base station; A specific antenna port from which a plurality of first reference signals are received or a specific directivity from which a plurality of first reference signals are received among a plurality of directivity patterns generated by a plurality of antenna ports Detection means for detecting a pattern, measurement means for measuring the reception power of each of the plurality of first reference signals, and reception power of each of the plurality of first reference signals, the plurality of first references There is provided a user apparatus comprising: a transmission unit that transmits the signal to the specific antenna port or the group for each specific directivity pattern to which the signal is received.

Description

The present invention relates to a user apparatus, a base station, and a communication method.

In LTE / LTE-Advanced, MIMO technology that increases system capacity, cell edge user throughput, and the like is employed. In addition, heterogeneous network technologies that reduce inter-cell interference and realize high-quality communication while mixing different types of base stations (macro cell, small cell, etc.) are being studied.

In particular, it is assumed that a small cell in a heterogeneous network uses a high frequency band. Here, since propagation loss increases in a high frequency band, in order to compensate for this, it is considered to apply massive MIMO that performs beam forming with a narrow beam width. Massive MIMO is also attracting attention as an elemental technology in the fifth generation radio technology.

Massive MIMO is a large-scale MIMO in which a large number of antennas (for example, 100 elements) are installed on the base station side, and the strength of the electric field can be concentrated in a narrow area, so that interference between users can be reduced. it can.

JP 2013-219507 A

FIG. 1 is a diagram illustrating an example of a communication environment where there are a large number of small cells to which massive MIMO is applied. As shown in FIG. 1, a large number of beams are transmitted from the base station of each small cell. When the user apparatus (UE) performs communication while moving in such an environment, the user apparatus selects a specific beam suitable for the current position and performs communication while sequentially switching the beam according to the movement. Further, by using a plurality of beams formed by massive MIMO at the same time, it is possible to perform communication by MIMO.

In order to realize such an operation, the user apparatus and the base station need to determine a plurality of beams that are candidates for MIMO communication.

FIG. 2 is a diagram for explaining the problem. In the example of FIG. 2A, the user apparatus receives two beams transmitted from a base station having a large number of antenna elements from the same direction. On the other hand, in the example of FIG.2 (b), the user apparatus has received two beams transmitted from the base station from a different direction, respectively.

Here, in order to improve the communication quality of communication by MIMO, it is desirable that the correlation between channels constituting the MIMO is lowered. That is, when the user apparatus performs MIMO transmission using a plurality of beams at the same time, as shown in FIG. 2A, the user apparatus does not perform MIMO transmission using a plurality of beams received from the same direction. As in b), it is desirable to perform MIMO transmission using a plurality of beams received from different directions.

The disclosed technique has been made in view of the above points, and is used for communication among a plurality of beams formed by a base station in a wireless communication system having a base station and a user apparatus that perform beam forming. An object is to provide a technique that allows a plurality of beams to be appropriately selected.

A user apparatus according to the disclosed technology is a user apparatus that communicates with the base station in a wireless communication system including the base station and the user apparatus, and receives a plurality of first reference signals transmitted from the base station. Of the plurality of directivity patterns generated by the first receiving means and the specific antenna port where the plurality of first reference signals are received or the plurality of antenna ports, the plurality of first reference signals Detection means for detecting a specific directivity pattern received, measurement means for measuring the reception power of each of the plurality of first reference signals, and reception power of each of the plurality of first reference signals. Transmitting means for transmitting to the base station divided into groups for each of the specific antenna port or the specific directivity pattern from which the plurality of first reference signals are received.

According to the disclosed technology, in a wireless communication system having a base station that performs beam forming and a user apparatus, a plurality of beams used for communication are appropriately selected from among a plurality of beams formed by the base station. It is possible to provide a technology that makes it possible.

It is a figure which shows the example of the communication environment where many small cells to which massive MIMO is applied exist. It is a figure for demonstrating a subject. It is a figure which shows the whole structure of the radio | wireless communications system which concerns on embodiment. It is a figure for demonstrating the structure of the beam used for communication, and each reference signal. It is a figure for demonstrating the structure of the beam used for communication. It is a figure which shows an example of the mapping of the discovery signal in embodiment. It is a figure which shows an example of a function structure of the user apparatus which concerns on embodiment. It is a figure which shows an example of a function structure of the small base station which concerns on embodiment. It is a figure which shows an example of the hardware constitutions of the user apparatus which concerns on embodiment. It is a figure which shows an example of the hardware constitutions of the small base station which concerns on embodiment. It is a figure for demonstrating the measuring method of the discovery signal which concerns on embodiment. It is a figure for demonstrating the number of the narrow beams which a user apparatus reports reception quality. It is a figure which shows an example of the process sequence of the mobile communication system which concerns on embodiment. It is a figure which shows an example of a structure of a reception quality report signal. It is a figure which shows an example of format information. It is a figure which shows an example of the modification of a structure of a reception quality report signal. It is a figure which shows an example of the modification of format information. It is a figure which shows an example of the signal in case format information is notified from a base station. It is a figure which shows an example of the modification (the 1) of a signal in case format information is notified from a base station. It is a figure which shows an example of the modification (the 2) of a signal when format information is notified from a base station. It is a figure for demonstrating the transmission method of a reception quality report signal and feedback information. It is a figure which shows an example of the format information to which the report pattern was provided. It is a figure which shows an example of the modification of the format information to which the report pattern was provided. It is a figure which shows an example of the transmission method of the discovery signal corresponding to a narrow beam.

Embodiments of the present invention will be described below with reference to the drawings. The embodiment described below is only an example, and the embodiment to which the present invention is applied is not limited to the following embodiment. For example, although the wireless communication system according to the present embodiment assumes a system based on LTE, the present invention is not limited to LTE and can be applied to other systems. In addition, in this specification and claims, “LTE” corresponds to not only a communication method corresponding to Release 8 or 9 of 3GPP but also Release 10, 11, 12, 13, or Release 14 or later of 3GPP. It is used in a broad sense that includes communication methods.

Further, in the present embodiment, the configuration of the reference signal of three layers is basically shown as an example, but the number of layers is not limited to this, the number of layers may be two, or the number of layers May be 4 or more.

<Overview>

(Overall configuration of wireless communication system)

FIG. 3 shows an overall configuration diagram of the radio communication system according to the embodiment. The radio communication system according to the present embodiment includes a macro base station 10 that forms a macro cell, and small base stations 11 and 12 that are within the coverage area of the macro cell. 3 shows a user apparatus 20 that communicates with the macro base station 10, the small base stations 11, 12, and the like.

In the radio communication system, macro coverage is ensured by the macro base station 10 in the low frequency band, and the traffic of the small area (eg, hot spot) is absorbed by the small base stations 11 and 12 in the high frequency band. Such frequency band allocation is merely an example, and the present invention is not limited to this.

The macro base station 10 and the small base stations 11 and 12 communicate with the user apparatus 20 through radio. The macro base station 10 and the small base stations 11 and 12 communicate with a CPU such as a processor, a memory device such as a ROM, a RAM, or a flash memory, an antenna for communicating with the user device 20, an adjacent base station, a core network, and the like. It is configured by hardware resources such as a communication interface device. The functions and processes of the macro base station 10 and the small base stations 11 and 12 may be realized by a processor processing or executing data or a program stored in the memory device. However, the macro base station 10 and the small base stations 11 and 12 are not limited to the hardware configuration described above, and may have any other appropriate hardware configuration.

The user apparatus 20 has a function of communicating with the macro base station 10, the small base stations 11, 12 and the core network or the like through radio. The user device 20 is, for example, a mobile phone, a smartphone, a tablet, a mobile router, or a wearable terminal. The user device 20 may be any user device 20 as long as the device has a communication function. The user apparatus 20 is a hardware resource such as a CPU such as a processor, a memory apparatus such as a ROM, a RAM, or a flash memory, an antenna for communicating with the macro base station 10 and the small base stations 11 and 12, and an RF (Radio Frequency) apparatus. Consists of. Each function and process of the user device 20 may be realized by a processor processing or executing data or a program stored in the memory device. However, the user device 20 is not limited to the hardware configuration described above, and may have any other appropriate hardware configuration.

The small base stations 11 and 12 in the present embodiment have a mass MIMO function, and can form various beams from a wide beam to a narrow beam. As shown in FIG. 3, in the present embodiment, a plurality of types of reference signals (reference signals) precoded by each small base station are transmitted by beams. Note that the reference signal is precoded means that in the example of transmission, the transmission signal is multiplied by a weight for each antenna port so that the reference signal is transmitted with a beam having a certain width. . For example, in the example illustrated in FIG. 3, the reference signal is transmitted from the small base station 11 using each of the beam 1-1, the beam 1-2, and the beam 1-3. In addition, reference signals are transmitted from the small base station 12 using the beam 2-1, the beam 2-2, and the beam 2-3.

The user apparatus 20 receives macro auxiliary information (Macro-Assisted Information) from the macro base station 10 in the coverage area of the macro cell (step 1), and uses the macro auxiliary information to transmit each beam of the small base stations 11 and 12. The reference signal transmitted in (1) is monitored (this is called a discovery signal), and a specific discovery signal is received (detected).

Here, it is assumed that the user apparatus 20 has received the discovery signal transmitted by each beam of the small base station 11. The user apparatus 20 measures reception quality (received power etc.) based on the received discovery signal, and transmits the measurement result to the small base station 11 (step 2). Then, based on the measurement report, the small base station 11 determines a beam on which the user apparatus 20 can receive a signal with the best quality (for example, the highest received power), and on the determined beam. , A reference signal (referred to as a measurement reference signal) is transmitted. The user apparatus 20 measures reception quality based on the measurement reference signal, generates feedback information (CSI (Channel State Information) or the like) to be notified to the small base station 11, and transmits the feedback information to the small base station 11.

The small base station 11 allocates radio resources for transmitting a data signal (PDSCH or the like) to the user apparatus 20 based on the feedback information received from the user apparatus 20.

Thus, the step of selecting the beam candidate used for communication using the discovery signal, the step of determining the best quality beam from the selected beam candidate as the beam used for communication, and The user apparatus 20 can receive a data signal from the small base station 11 by sequentially performing an operation of assigning radio resources based on feedback information for the beam.

(Beam identification method)

Next, a method for identifying a beam used for communication in the wireless communication system according to the present embodiment will be described with reference to FIGS.

FIG. 4 is a diagram for explaining a configuration of a beam used for communication and each reference signal. FIG. 5 is a diagram for explaining a configuration of a beam used for communication.

As shown in FIG. 4, the reference signal in the present embodiment has a hierarchical structure, and the user apparatus 20 refers to the reference signal in the lower hierarchy sequentially from the reference signal in the higher hierarchy, thereby enabling the small base station It is possible to detect an optimum beam among a plurality of beams transmitted from 11, 12 and receive a desired data signal using the beam. By adopting such a hierarchical structure, beam candidates can be narrowed down efficiently, and optimal beam detection and switching can be performed quickly without searching for a large number of beam reference signals. It is.

More specifically, in the example shown in FIG. 4, there is macro auxiliary information as the first layer. As described above, the macro auxiliary information is transmitted from the macro base station 10 to the user apparatus 20 in the macro coverage, and the user apparatus 20 receives the discovery signal using the macro auxiliary information.

The macro auxiliary information includes, for example, radio resource information (timing, frequency, etc.) to which the discovery signal is transmitted, discovery signal sequence information, and the like. The channel through which the macro base station 10 transmits the macro auxiliary information is not limited to a specific type of channel, but is transmitted using, for example, a control channel, a broadcast channel, or a data channel defined by LTE.

In a wireless communication system, there are a plurality of macro base stations, but the user apparatus 20 may search in a macro cell in which the user apparatus 20 is located by referring to the macro auxiliary information. It is possible to grasp information of discovery signals to be performed. That is, the user apparatus 20 can specify the branch A in FIG. 4 based on the macro auxiliary information.

Since the macro auxiliary information is a signal that is referred to (referenced) by the user apparatus 20, it can be called a kind of reference signal.

There is a discovery signal as the second layer. The discovery signal is pre-coded and is a small base for both a wide beam (hereinafter referred to as “broad beam”) and a beam transmitted with a narrower width than the wide beam (hereinafter referred to as “narrow beam”). This is a signal transmitted from the stations 11 and 12. The wide beam is, for example, a plurality of beams transmitted in a relatively wide range as shown on the left side of FIG. Narrow beams are a plurality of beams transmitted with a narrower width than a wide beam, for example, as shown in the center and right side of FIG.

Discovery signals are transmitted from each of the small base stations 11 and 12 using a plurality of wide beams and a plurality of narrow beams, and the user apparatus 20 monitors the discovery signals included in the wide beams based on the macro auxiliary information. And receive (detect). When detecting the discovery signal included in the wide beam, the user device 20 searches for the discovery signal corresponding to the narrow beam. When receiving (detecting) the discovery signal corresponding to the narrow beam, the user apparatus 20 measures the reception quality (received power, etc.) of the discovery signal corresponding to the detected one or more narrow beams, and sends the measurement result to the base station. Send. In the present embodiment, unless otherwise specified, the term “reception quality” is used in a broad sense including reception power.

In the example of FIG. 4, for example, in the second hierarchy, it is possible to select B branches (corresponding to different wide beams in each of the B branches) under the A branch by the discovery signal included in the wide beam. become. In addition, the discovery signal corresponding to each narrow beam enables selection of C branches (corresponding to narrow beams in which each of the C branches is different) under the B branch. Further, in the example of FIG. 5, the branch of B corresponds to each of the plurality of wide beams shown on the left side of FIG. 5, and the branch of C corresponds to each of the plurality of narrow beams shown in the center of FIG. Equivalent to.

Note that information (series, etc.) on the discovery signal is associated with each wide beam and each narrow beam. The information may be referred to as “identifier”. That is, the user apparatus 20 measures reception quality (reception power, etc.) of discovery signals associated with a plurality of different identifiers transmitted from the base station. In the following description, an identifier associated with a wide beam is referred to as “beam group ID”, and an identifier associated with a narrow beam is referred to as “beam ID”. A wide beam can be uniquely identified by the beam group ID, and a narrow beam can be uniquely identified by the beam ID.

As the third layer, there is a measurement reference signal. The measurement reference signal is a signal transmitted from the small base stations 11 and 12 in a narrow beam. The small base stations 11 and 12 determine the narrow beam for transmitting the measurement reference signal based on the reception quality (reception power or the like) of the discovery signal corresponding to one or more narrow beams reported from the user apparatus 20. For example, the small base stations 11 and 12 can make a plurality of narrow beams in order from the largest received power into narrow beams that transmit measurement reference signals.

Subsequently, the small base stations 11 and 12 transmit a measurement reference signal for each determined narrow beam. The user apparatus 20 receives each measurement reference signal, measures reception quality (reception power, etc.), and provides feedback information (eg, identification information of the measurement reference signal with the highest received power) as a small base station. 11 and 12 are returned. The small base stations 11 and 12 that have received the feedback information perform link adaptation, rank adaptation, scheduling, and the like for the downlink data signal based on the feedback information.

In the example illustrated in FIG. 4, for example, if the small base station 11 selects two branches indicated by D as narrow beams for transmitting the measurement reference signal, the user apparatus 20 is included in the two narrow beams. The reception quality of the measurement reference signal is measured, and feedback information is transmitted to the small base station 11. The user apparatus 20 receives the data signal transmitted from the small base station 11 with the two narrow beams. Further, in the example of FIG. 5, as illustrated on the right side of FIG. 5, the user apparatus 20 transmits the data signal transmitted from the small base station 11 to two narrow beams (beams corresponding to D in FIG. 5). Will be received.

The small base stations 11 and 12 further select a narrow beam used for communication with the user apparatus 20 based on the feedback information received from the user apparatus 20 (for example, from among the beams corresponding to D in FIG. 5). Further, a narrow beam may be selected).

(Configuration example of each signal)

In the present embodiment, the discovery signal included in the wide beam may be used for the user apparatus 20 to synchronize with the small base stations 11 and 12. Therefore, in the present embodiment, the discovery signal included in the wide beam can also be called a “synchronization signal”. For the discovery signal included in the wide beam, for example, PSS (Primary Synchronization signal) / SSS (Secondary Synchronization signal) which is a synchronization signal may be used.

In the present embodiment, the discovery signal corresponding to the narrow beam may be a predetermined reference signal, for example, because the user apparatus 20 is used for measuring the reception quality for each narrow beam.

FIG. 6 is a diagram illustrating an example of discovery signal mapping in the embodiment. As shown in FIG. 6, for example, PSS and SSS used for discovery signals included in wide beams are mapped to the center of the system band, and discovery signals corresponding to a plurality of narrow beams are mapped above and below PSS and SSS. You may make it do. In the example of FIG. 6, the discovery signals mapped above and below the PSS and SSS have the same sequence.

An example of signal mapping in each block (time length is one symbol) is shown on the right side of FIG. In the example on the right side of FIG. 6, the number indicates a beam (narrow beam discovery signal) for transmitting a signal with the corresponding resource. In the example on the right side of FIG. 6, eight narrow beam discovery signals are distributed and mapped to subcarriers. Note that the discovery signal in the embodiment is not limited to the example shown in FIG. A signal or mapping method different from that in FIG. 6 may be used.

In the present embodiment, for example, CSI-RS (Channel State Information-Reference Signal) may be used as the measurement reference signal.

As described above, the outline of the mobile communication system according to the present embodiment has been described with reference to FIGS. 4 to 6. However, in the present embodiment, as shown in the above-described problem, communication by MIMO using a plurality of beams simultaneously. To achieve a low correlation (ie, spatially separated) between the two narrow beams shown in FIGS. 4 and 5 (the beam corresponding to D in FIG. 5). Try to select a beam. Specifically, when measuring the reception quality of the discovery signal corresponding to the narrow beam corresponding to the branch C in FIGS. 4 and 5, the user apparatus 20 identifies and measures the direction in which the narrow beam is received. The received quality is divided into groups for each direction in which the narrow beam is received and transmitted to the small base stations 11 and 12.

Further, when determining the narrow beam for transmitting the measurement reference signal, the small base stations 11 and 12 do not simply determine the plurality of narrow beams in order of good reception quality, but determine the plurality of narrow beams determined. A plurality of narrow beams are determined so that are distributed in groups in different directions. By determining a plurality of narrow beams for transmitting the measurement reference signal in this way, the correlation between the plurality of narrow beams used for communication becomes low, and it becomes possible to improve throughput by MIMO spatial multiplexing. .

In the following description, the small base stations 11 and 12 are collectively referred to as the small base station 11.

<Functional configuration>

(User device)

FIG. 7 is a diagram illustrating an example of a functional configuration of the user apparatus according to the embodiment. As illustrated in FIG. 7, the user device 20 includes a signal reception unit 101, a signal transmission unit 102, a reception quality measurement unit 103, and a feedback information generation unit 104. In addition, the signal reception unit 101 includes a reception direction detection unit 111. FIG. 7 shows only functional units that are particularly related to the embodiment of the present invention in the user apparatus 20, and has at least a function (not shown) for performing an operation based on LTE. Further, the functional configuration shown in FIG. 7 is merely an example. As long as the operation according to the present embodiment can be performed, the function classification and the name of the function unit may be anything.

The signal receiving unit 101 acquires upper layer information from a lower layer signal received wirelessly. The signal receiving unit 101 acquires macro auxiliary information from a control signal or the like received from the macro base station 10, stores the macro auxiliary information, and based on the stored macro auxiliary information, the small base station 11 Receiving (detecting) a discovery signal included in a wide beam transmitted from. Further, the signal receiving unit 101 performs symbol timing synchronization and radio frame synchronization using a discovery signal included in a wide beam, for example, specifies a signal sequence at the same time, and detects a discovery signal corresponding to a narrow beam according to the identified signal sequence Is received (detected). Further, the signal receiving unit 101 receives a measurement reference signal transmitted from the small base station 11.

The signal transmission unit 102 generates a lower layer signal from the upper layer information and transmits it wirelessly. In addition, the signal transmission unit 102 transmits the reception quality measured by the reception quality measurement unit 103 to the small base station 11. In addition, the signal transmission unit 102 transmits the feedback information generated by the feedback information generation unit 104 to the small base station 11.

The reception quality measurement unit 103 measures the reception quality (reception power etc.) of the discovery signal corresponding to the narrow beam. More specifically, the reception quality measurement unit 103 identifies the beam ID of each narrow beam from the discovery signal corresponding to the narrow beam, measures the reception quality of the narrow beam corresponding to the identified beam ID, and transmits the signal transmission unit. 102. Further, the reception quality measurement unit 103 acquires the reception direction of the narrow beam, the specific directivity pattern where the narrow beam is received, the specific antenna port where the narrow beam is received, or the like from the reception direction detection unit 111. Thus, the reception direction of the narrow beam whose reception quality is measured is grasped. The reception quality measurement unit 103 measures the reception quality (reception power, etc.) of the discovery signal corresponding to the narrow beam based on an instruction from the small base station 11 or at a predetermined cycle, and the measured reception quality is transmitted as a signal. You may make it transmit to the small base station 11 via the part 102. FIG.

The feedback information generation unit 104 generates feedback information based on the measurement result obtained from the measurement reference signal corresponding to the narrow beam, and passes the feedback information to the signal transmission unit 102. The feedback information may include CSI such as a rank indicator (RI), a precoding matrix indicator (PMI), and a channel quality indicator (CQI). Note that the feedback information generation unit 104 may pass feedback information on all narrow beams including the measurement reference signal to the signal transmission unit 102, or may be predetermined in the order of good or bad reception quality of the narrow beams. The number of narrow beam feedback information may be passed to the signal transmission unit 102. The feedback information generation unit 104 generates feedback information based on an instruction from the small base station 11 or by measuring a measurement reference signal included in the narrow beam at a predetermined period, and transmits the generated feedback information to the signal transmission You may make it transmit to the small base station 11 via the part 102. FIG.

The reception direction detection unit 111 detects a direction in which a narrow beam is received by forming a beam on the reception side using a plurality of antennas of the user apparatus 20. In addition, the reception direction detection unit 111 notifies the reception quality measurement unit 103 of the reception direction of the detected narrow beam. Forming a beam on the receiving side means that a received signal is multiplied by a weight for each antenna port of the user apparatus 20 so that a narrow beam is received with a beam having a certain width (that is, with directivity). To generate sex patterns. In addition, the reception direction detection unit 111 may notify the reception quality measurement unit 103 of a specific directivity pattern in which a narrow beam is received instead of the reception direction of the narrow beam. The weight multiplied for each antenna port may be specified by a code book.

Further, the reception direction detection unit 111 may detect the reception direction of the narrow beam by specifying which antenna port from which the narrow beam is received among the plurality of antenna ports of the user apparatus 20. Good. For example, it is assumed that the reception direction can be specified by the shape of the physical antenna provided in the user apparatus 20. In this case, the reception direction detection unit 111 may notify the reception quality measurement unit 103 of a specific antenna port through which the narrow beam is received instead of the reception direction of the narrow beam.

(Small base station)

FIG. 8 is a diagram illustrating an example of a functional configuration of the small base station according to the embodiment. As illustrated in FIG. 8, the small base station 11 includes a signal reception unit 201, a signal transmission unit 202, a beam candidate selection unit 203, and a beam control unit 204. FIG. 8 shows only functional units that are particularly related to the embodiment of the present invention in the small base station 11, and has at least a function (not shown) for performing an operation based on LTE. The functional configuration shown in FIG. 8 is only an example. As long as the operation according to the present embodiment can be performed, the function classification and the name of the function unit may be anything.

The signal reception unit 201 acquires information on the upper layer from the lower layer signal received wirelessly. In addition, the signal reception unit 201 passes the reception quality of each narrow beam received from the user apparatus 20 to the beam candidate selection unit 203. Further, the signal receiving unit 201 passes the narrow beam feedback information received from the user apparatus 20 to the beam control unit 204.

The signal transmission unit 202 generates a lower layer signal from the upper layer information and transmits the generated signal wirelessly. The signal transmission unit 202 transmits a radio signal so that a wide beam and a narrow beam including a discovery signal are formed by beam forming realized by multiplying each antenna port by a predetermined weight. Further, the signal transmission unit 202 transmits a measurement reference signal from the instructed narrow beam based on an instruction from the beam candidate selection unit 203. Further, the signal transmission unit 202 assigns radio resources for transmitting a data signal (PDSCH or the like) to the user apparatus 20 with respect to the instructed narrow beam based on an instruction from the beam control unit 204.

The beam candidate selection unit 203 selects one or more narrow beam candidates used for communication with the user apparatus 20 based on the reception quality of each narrow beam for each reception direction notified from the user apparatus 20. For example, the beam candidate selection unit 203 may select one narrow beam with the best reception quality for each reception direction, or a predetermined number of narrow beams in the order of good reception quality for each reception direction. A beam may be selected. In addition, when there are narrow beams with good reception quality only in a specific reception direction, a predetermined number of narrow beams are selected in order of good reception quality among narrow beams received from the specific reception direction. You may do it. There are various methods for selecting one or more narrow beam candidates used for communication with the user apparatus 20. That is, the beam candidate selection unit 203 is not limited to the selection method described above, and may select narrow beam candidates by another selection method.

Further, the beam candidate selection unit 203 instructs the signal transmission unit 202 to transmit the measurement reference signal from the selected one or more narrow beams. For example, the beam candidate selection unit 203 selects an antenna port included in the small base station 11 so that the measurement reference signal is transmitted from one or more selected narrow beams, and weights multiplied by the antenna ports. And instructing the signal transmission unit 202.

The beam control unit 204 controls the antenna port provided in the small base station 11 based on the narrow beam feedback information received from the user apparatus 20, for example, MIMO spatial multiplexing using a plurality of narrow beams, transmission diversity, etc. To realize. Further, the beam control unit 204 switches the optimum narrow beam used for communication sequentially (performs beam tracking) according to the movement of the user apparatus 20 based on the narrow beam feedback information received from the user apparatus 20. Also good. These controls may be performed by the beam control unit 204 and the signal transmission unit 202 working together.

The functional configurations of the user apparatus 20 and the small base station 11 described above may be realized entirely by hardware circuits (for example, one or a plurality of IC chips), or may be partially configured by hardware circuits. Other portions may be realized by a CPU and a program.

(User device)

FIG. 9 is a diagram illustrating an example of a hardware configuration of the user apparatus according to the embodiment. FIG. 9 shows a configuration closer to the mounting example than FIG. As illustrated in FIG. 9, the user apparatus 20 performs processing such as an RF (Radio Frequency) module 301 that performs processing related to a radio signal, a BB (Base Band) processing module 302 that performs baseband signal processing, and a higher layer. UE control module 303.

The RF module 301 should transmit from the antenna by performing D / A (Digital-to-Analog) conversion, modulation, frequency conversion, power amplification, etc. on the digital baseband signal received from the BB processing module 302 Generate a radio signal. In addition, a digital baseband signal is generated by performing frequency conversion, A / D (Analog to Digital) conversion, demodulation, and the like on the received radio signal, and the digital baseband signal is passed to the BB processing module 302. The RF module 301 includes, for example, a part of the signal reception unit 101 and a part of the signal transmission unit 102 illustrated in FIG.

The BB processing module 302 performs processing for mutually converting an IP packet and a digital baseband signal. A DSP (Digital Signal Processor) 312 is a processor that performs signal processing in the BB processing module 302. The memory 322 is used as a work area for the DSP 312. The BB processing module 302 includes, for example, a part of the signal reception unit 101, a part of the signal transmission unit 102, a reception quality measurement unit 103, and a feedback information generation unit 104 shown in FIG.

The UE control module 303 performs IP layer protocol processing, various application processing, and the like. The processor 313 is a processor that performs processing performed by the UE control module 303. The memory 323 is used as a work area for the processor 313.

(Small base station)

FIG. 10 is a diagram illustrating an example of a hardware configuration of the small base station according to the embodiment. FIG. 10 shows a configuration closer to the mounting example than FIG. As shown in FIG. 8, the small base station 11 includes an RF module 401 that performs processing related to a radio signal, a BB processing module 402 that performs baseband signal processing, a device control module 403 that performs processing such as an upper layer, a network And a communication IF 404 that is an interface for connecting to the communication terminal.

The RF module 401 generates a radio signal to be transmitted from the antenna by performing D / A conversion, modulation, frequency conversion, power amplification, and the like on the digital baseband signal received from the BB processing module 402. In addition, a digital baseband signal is generated by performing frequency conversion, A / D conversion, demodulation, and the like on the received radio signal, and passed to the BB processing module 402. The RF module 401 includes, for example, a part of the signal reception unit 201 and a part of the signal transmission unit 202 illustrated in FIG.

The BB processing module 402 performs processing for mutually converting an IP packet and a digital baseband signal. The DSP 412 is a processor that performs signal processing in the BB processing module 402. The memory 422 is used as a work area for the DSP 412. The BB processing module 402 includes, for example, a part of the signal reception unit 201, a part of the signal transmission unit 202, a part of the beam candidate selection unit 203, and a part of the beam control unit 204 shown in FIG.

The device control module 403 performs IP layer protocol processing, OAM (Operation and Maintenance) processing, and the like. The processor 413 is a processor that performs processing performed by the device control module 403. The memory 423 is used as a work area for the processor 413. The auxiliary storage device 433 is, for example, an HDD or the like, and stores various setting information and the like for the small base station 11 itself to operate. The apparatus control module 403 includes, for example, a part of the beam candidate selection unit 203 and a part of the beam control unit 204 shown in FIG.

<Processing procedure>

(Receiving quality measurement method and reporting method)

FIG. 11 is a diagram for explaining a discovery signal measurement method according to the embodiment. As illustrated in FIG. 11, the user apparatus 20 measures the reception quality of the narrow beam discovery signal for each reception direction for each narrow beam arriving from each reception direction (A to D in FIG. 11), and the small base station 11. To report to.

The user apparatus 20 groups one or more narrow beams coming from each reception direction for each reception direction. For example, the user apparatus 20 groups a group of one or more narrow beams received from the reception direction A as a beam set # 1, and groups one or more narrow beams received from the reception direction B into a beam set # 2. And one or more narrow beam groups received from the receiving direction C are grouped as a beam set # 3. Although not shown in FIG. 11, if there are one or more narrow beams received from the reception direction D, these narrow beams are grouped as a beam set # 4.

By being grouped in this way, the small base station 11 has received the reception quality of the discovery signal of each narrow beam in the same reception direction in the user apparatus 20 or in different reception directions. Can be determined.

Note that the user apparatus 20 does not necessarily have to make the reception directions A to D correspond to the beam sets # 1 to # 4, respectively. For example, the user apparatus 20 sets the beam set # 1 for the reception direction in which a narrow beam with the best reception quality (reception power, etc.) exists among all the narrow beam discovery signals received from each reception direction. May be associated with each other. Further, the user apparatus 20 may associate the beam set # 2 with a reception direction in which a narrow beam having a good reception quality (reception power or the like) exists next. This is because the small base station 11 does not particularly know in which reception direction (for example, the upper surface direction of the terminal or the right direction) the narrow beam is received. This is because it is possible to select a narrow beam candidate for use in downlink communication if it can be discriminated.

FIG. 12 is a diagram for explaining the number of narrow beams for which the user apparatus reports reception quality. For example, the user apparatus 20 measures the reception quality of discovery signals corresponding to one or more narrow beams grouped by reception direction, and sets the reception quality that satisfies a predetermined condition among the measured one or more reception qualities. Only the small base station 11 may be reported. The user apparatus 20 does not report the reception quality regarding the narrow beam with poor reception quality (that is, the narrow beam that is unlikely to be used for communication in the end), so that the user apparatus 20 transmits the small quality information to the small base station 11. It becomes possible to reduce the data amount of the signal transmitted to the.

A specific example will be described with reference to FIGS. The horizontal axis in FIG. 12 indicates a beam ID for uniquely identifying a narrow beam, and the vertical axis indicates the magnitude of RSRP (Reference Signal Received Power). T represents a predetermined range. For example, FIG. 12 assumes that the user apparatus 20 represents the measurement result of the reception power (RSRP) of discovery signals corresponding to a plurality of narrow beams received from the reception direction A of FIG. For example, the user apparatus 20 selects a narrow beam (A in FIG. 12) having the largest received power, and the narrow beam that is received power within a predetermined range (T) from the received power of the selected narrow beam (A). (B to E in FIG. 12) are further selected. Subsequently, the user apparatus 20 transmits the received power regarding the selected narrow beams A to E and the beam ID of each narrow beam to the small base station 11 together with information for identifying the group of the beam set # 1.

The predetermined range (T) may be set in advance in the user apparatus 20, for example, or may be notified to the user apparatus 20 in advance using a macro cell control signal, broadcast information, or the like. It may be.

Further, the user apparatus 20 measures reception quality of discovery signals corresponding to one or more narrow beams grouped by reception direction, and the small base is limited to a predetermined number among the measured one or more reception qualities. It may be transmitted to the station 11. For example, when the predetermined number is “5”, the user apparatus 20 smallly receives the reception qualities regarding the five narrow beams in the order of the highest reception quality among the reception qualities regarding the plurality of narrow beams received from the reception direction A. You may make it transmit to the base station 11. FIG.

Further, the user apparatus 20 may limit the total upper limit number of reception quality transmitted to the small base station 11. For example, the reception quality for 5 narrow beams is measured in the group of beam set # 1, the reception quality for 6 narrow beams is measured in the group of beam set # 2, and 7 receptions in the group of beam set # 3. Assume that the reception quality for a narrow beam has been measured. When the upper limit number is 10, the user apparatus 20 transmits only the reception quality related to the 10 narrow beams to the small base station 11 in the order of good reception quality among the reception quality related to the 18 narrow beams. It may be. It becomes possible to reduce the data amount of the signal transmitted from the user apparatus 20 to the small base station 11.

(Processing sequence)

FIG. 13 is a diagram illustrating an example of a processing sequence of the mobile communication system according to the embodiment. A series of processing sequences from when the user apparatus 20 finds a wide beam and a narrow beam until data transmission is performed from the small base station 11 to the user apparatus 20 will be described with reference to FIG. Note that the user apparatus 20 receives macro auxiliary information from the macro base station in advance or holds auxiliary information corresponding to the macro auxiliary information in advance. That is, the user apparatus 20 preliminarily finds information for finding a wide beam (frequency band, bandwidth, transmission timing and sequence of each discovery signal, etc.), and information on the transmission timing and sequence of discovery signal corresponding to a narrow beam. Assume that

In step S301, the signal transmission unit 202 of the small base station 11 obtains a plurality of precoded discovery signals that form a wide beam and a plurality of precoded discovery signals that form a narrow beam, as described above. Sending.

In step S <b> 302, the signal reception unit 101 of the user apparatus 20 receives the discovery signal included in the wide beam based on the macro auxiliary information or auxiliary information corresponding thereto, and performs frequency synchronization with the small base station 11. At the same time, timing synchronization (symbol synchronization, frame synchronization, etc.) is performed. Note that the user apparatus 20 may receive information (minimum system information and the like) necessary for communication in the coverage of the small base station 11 by the discovery signal included in the wide beam. Subsequently, the user apparatus 20 specifies the beam ID of the narrow beam that can receive the discovery signal by searching the discovery signal corresponding to the narrow beam according to the signal sequence specified by the discovery signal included in the wide beam. . For example, when the discovery signal corresponding to the narrow beam has a format as shown in FIG. 6, the signal receiving unit 101 determines the receivable narrow beam based on the receivable narrow beam OFDM symbol and the position of the subcarrier. It is possible to specify the beam ID.

Subsequently, the reception quality measurement unit 103 of the user device 20 measures the reception quality of the discovery signal corresponding to the receivable narrow beam. At this time, for example, the reception quality measurement unit 103 may notify the reception direction of the detected narrow beam discovery signal from the reception direction detection unit 111, or the reception direction detection unit 111 may determine the reception direction. You may make it search for the discovery signal corresponding to a narrow beam, after narrowing down. Thereby, the user apparatus 20 can measure the reception quality of the discovery signal corresponding to each narrow beam while specifying the beam ID of the narrow beam that can be received for each reception direction.

In step S <b> 303, the signal transmission unit 202 of the small base station 11 transmits information regarding the assigned radio resource to the user apparatus 20 in order to cause the user apparatus 20 to transmit reception quality of the discovery signal corresponding to each narrow beam. The processing procedure in step S303 is, for example, that the user apparatus 20 allocates uplink radio resources to the small base station 11 by a random access procedure, PUCCH (Physical Uplink Control Channel), EPUCCH (Enhanced Physical Uplink Control Channel), or the like. For example, it may be performed by requesting the small base station 11 to allocate uplink radio resources via the macro base station. The small base station 11 may voluntarily allocate uplink radio resources according to the timing of transmitting the discovery signal in step S301.

In step S304, the signal transmission unit 102 of the user apparatus 20 transmits the reception quality report signal to the small base station 11, thereby reporting the reception quality of the discovery signal corresponding to the narrow beam measured in step S302. For example, an uplink physical control channel (PUCCH / EPUCCH) or a random access channel (PRACH) defined by LTE is used as an uplink channel by which the signal transmission unit 102 of the user apparatus 20 transmits a reception quality report signal. However, it is not limited to this.

Here, a signal format used for the reception quality report signal will be described.

FIG. 14 is a diagram illustrating an example of a configuration of a reception quality report signal. As shown in FIG. 14, the reception quality report signal includes “format information”, “beam ID and reception quality (RSRP)” of each discovery signal corresponding to each narrow beam, and “CRC (Cyclic Redundancy Check)”. And have.

The “format information” stores information indicating which beam set each beam ID and reception quality (RSRP) of the discovery signal corresponding to each narrow beam corresponds to. “CRC” is a UEID (eg, for example) that identifies the user apparatus 20 with respect to the CRC calculated based on the format information and the beam ID and reception quality (RSRP) of each discovery signal corresponding to each narrow beam. It is calculated by masking with C-RNTI (Cell-Radio Network Temporary Identifier) (for example, taking XOR).

In other words, “format information” corresponds to header information, and “beam ID and reception quality (RSRP)” corresponds to a data part.

Note that the signal transmission unit 102 of the user apparatus 20 encodes the reception quality report signal illustrated in FIG. 14 and transmits the encoded reception quality report signal to the user apparatus 20. Here, as an encoding method, for example, a method of encoding (Joint Coding) “format information”, “beam ID and reception quality (RSRP)”, and “CRC” together can be considered.

As another method, for example, a method of separately encoding (separate coding) “format information”, “beam ID and reception quality (RSRP)”, and “CRC” is conceivable. Thereby, for example, the small base station 11 can refer to the header information (“format information”) and the data part (“beam ID and reception quality (RSRP)”) separately.

FIG. 15 is a diagram illustrating an example of format information. As shown in FIG. 15, the format information can have a plurality of forms. First, the “number of beam sets” is first stored in the format information of FIG. 15A, and “the number of beams of beam set #N” is repeatedly stored according to the number of beam sets. For example, in the format information of FIG. 15A, “number of beam sets” is 2, “number of beams of beam set # 1” is 2, and “number of beams of beam set # 2” is 3. In this case, among the five “beam IDs and reception qualities” stored subsequent to the format information, the first two are information related to beam set # 1, and the next three “beam IDs” are stored. "Receiving quality" means that the information is related to beam set # 2. The format information in FIG. 15A has the advantage that the number of beam sets that can be stored is not limited, although the size of the format information is increased.

Next, the format information in FIG. 15B stores “the number of beams of beam set # 1” and “the number of beams of beam set # 2”. When the format information of FIG. 15B is used, the user apparatus 20 can report only information on two beam sets, but has an advantage that the format size can be prevented from becoming unlimited. When the format information in FIG. 15B is used, if there is only one beam set to be reported from the user apparatus 20 (that is, a narrow beam is received only in a specific reception direction), The user apparatus 20 may set “zero number of beams of beam set # 2” to zero. Further, in the format information of FIG. 15B, information regarding three or more beam sets may be stored. For example, “number of beams of beam set # 1”, “number of beams of beam set # 2”, and “number of beams of beam set # 3” may be stored in the format information.

Next, “total number of beams” and “number of beams of beam set # 1” are stored in the format information of FIG. In the format information of FIG. 15C, the number of beams of the beam set # 2 can be obtained by calculating “total number of beams” − “number of beams of the beam set # 1”. Further, when the same number is set in the “total number of beams” and the “number of beams of beam set # 1”, it means that there is only one beam set reported from the user apparatus 20. When the format information in FIG. 15C is used, the user apparatus 20 can report only information related to two beam sets as in FIG. 15B, but can avoid an unlimited increase in format size. There is an advantage.

Next, “number of beam sets” and “total number of beams” are stored in the format information of FIG. For example, when the “number of beam sets” is 3 and the “total number of beams” is 9, the reception quality report signal stores three “beam IDs and reception quality” for each beam set. Will mean. When the format information of FIG. 15D is used, the user apparatus 20 reports information on a plurality of beam sets although the number of “beam IDs and reception qualities” reported in each beam set needs to be the same. There is an advantage that the format size can be prevented from being increased without limit.

Subsequently, a modification of the signal format of the reception quality report signal will be described. FIG. 16 is a diagram illustrating an example of a modification of the configuration of the reception quality report signal. As shown in FIG. 16, the reception quality report signal includes “format information”, “beam set ID” for identifying beam sets (# 1 to #N), and “discovery signal” corresponding to each narrow beam. Beam ID and reception quality (RSRP) "and" CRC ".

The “format information” stores information indicating how many beam IDs and reception quality (RSRP) of discovery signals corresponding to each narrow beam are stored in the reception quality report signal. “CRC” identifies the user apparatus 20 with respect to the CRC calculated based on the format information, the beam set ID, and the beam ID and reception quality (RSRP) of each discovery signal corresponding to each narrow beam. It is calculated by masking with UEID (for example, C-RNTI) to be performed (for example, taking XOR).

In other words, “format information” corresponds to header information, and “beam set ID” and “beam ID and reception quality (RSRP)” correspond to a data part.

Note that the signal transmission unit 102 of the user apparatus 20 may encode the reception quality report signal illustrated in FIG. 16 and transmit the encoded reception quality report signal to the user apparatus 20. Here, as a coding method, for example, a method of collectively coding (Joint Coding) “format information”, “beam set ID”, “beam ID and reception quality (RSRP)”, and “CRC” is conceivable.

As another method, for example, a method of separately encoding (separate coding) “format information”, “beam set ID”, “beam ID and reception quality (RSRP)”, and “CRC” is conceivable. . Thereby, for example, the small base station 11 can refer to the header information (“format information”) and the data part (“beam set ID” and “beam ID and reception quality (RSRP)”) separately. become.

FIG. 17 is a diagram illustrating an example of a modification of the format information. The format information shown in FIG. 17 may be applied, for example, when the reception quality report signal has a configuration as shown in FIG. As shown in FIG. 17, the format information can have a plurality of forms. First, “total number of beams” is stored in the format information of FIG. For example, in the format information of FIG. 17A, when the “total number of beams” is 4, there are 4 pairs of “beam set ID” and “beam ID and reception quality” stored subsequent to the format information. It means that Thereby, the format information in FIG. 17A has an advantage that the format size can be prevented from becoming unlimited.

Next, “total number of beams” and “number of beam sets” are stored in the format information of FIG. For example, in the format information of FIG. 17B, when the “total number of beams” is 4 and the “number of beam sets” is 2, the “beam set ID” and “ This means that there are four pairs of “beam ID and reception quality”, and “beam ID and reception quality” of the two beam sets are included in the reception quality report signal. The format information in FIG. 17B has an advantage that the format size can be prevented from becoming unlimited as in the case of FIG. 17A. Hereinafter, returning to FIG.

In step S305, the beam candidate selection unit 203 of the small base station 11 determines, based on the reception quality of the discovery signal corresponding to the narrow beam stored in the reception quality report signal received in the processing procedure of step S304, One or more narrow beam candidates to be used for the communication are selected. Here, for example, the beam candidate selection unit 203 selects, for each of a plurality of beam sets included in the reception quality report signal, one by one in order from the narrow beam having the best reception quality (reception power, etc.). Specifically, the beam candidate selection unit 203 selects, for example, one narrow beam having the best reception quality from a plurality of narrow beams reported as the beam set # 1, and then reports as the beam set # 2. One narrow beam having the best reception quality is selected from the plurality of narrow beams. By repeatedly performing such processing, the beam candidate selection unit 203 may select three or more narrow beams.

The beam candidate selection unit 203 may further use an SRS (Sounding Reference Signal) received from the user apparatus 20 when selecting one or more narrow beam candidates used for communication with the user apparatus 20. Good.

In step S306, the signal transmission unit 202 of the small base station 11 transmits the measurement reference signal via the narrow beam selected in the processing procedure of step S305.

In step S307, the feedback information generation unit 104 of the user apparatus 20 generates feedback information based on the measurement result obtained from the measurement reference signal corresponding to each narrow beam. As described above, the feedback information includes, for example, CSI such as a rank indicator (RI), a precoding matrix indicator (PMI), and a channel quality indicator (CQI). Also good.

In step S <b> 308, the signal transmission unit 202 of the small base station 11 transmits information on the assigned radio resource to the user apparatus 20 in order to cause the user apparatus 20 to transmit feedback information. Note that the processing procedure in step S308 is similar to the processing procedure in step S303, for example, when the user apparatus 20 requests the small base station 11 to allocate uplink radio resources by a random access procedure or PUCCH, EPUCCH, or the like. It may be performed. The small base station 11 may voluntarily allocate uplink radio resources according to the timing of transmitting the discovery signal in step S306.

In step S309, the signal transmission unit 102 of the user apparatus 20 transmits the feedback information generated in the processing procedure of step S307 to the small base station 11. As an uplink channel through which the signal transmission unit 102 of the user apparatus 20 transmits feedback information, for example, an uplink physical control channel (PUCCH / EPUCCH) or a random access channel (PRACH) defined by LTE can be used. Is not limited to this.

In step S310, the beam control unit 204 of the small base station 11 determines a narrow beam used for transmitting downlink data to the user apparatus 20 based on the feedback information received in the processing procedure of step S309.

In step S311, the beam control unit 204 and the signal transmission unit 202 of the small base station 11 perform scheduling based on the feedback information, and a beam, rank, MCS (modulation scheme / coding rate), resource suitable for the user apparatus 20 Etc., and the antenna port is appropriately controlled to transmit a data signal to the user apparatus 20.

Note that the mobile communication system according to the embodiment, when recognizing the reception direction of the discovery signal in the processing procedure of step S302 to step S304 shown in FIG. You may make it recognize the specific antenna port from which a discovery signal is received.

Note that the mobile communication system according to the embodiment may repeatedly perform the processing procedures in steps S301 to S305 shown in FIG. 13 at predetermined intervals. Thereby, the small base station 11 can change one or more narrow beam candidates used for communication with the user apparatus 20 as necessary.

In addition, the mobile communication system according to the embodiment may repeatedly perform the processing procedures in steps S306 to S311 illustrated in FIG. 13 at predetermined intervals. For example, the small base station 11 is used to transmit downlink data to the user apparatus 20 based on feedback information corresponding to a plurality of narrow beams by repeatedly performing the processing procedure of Steps S306 to S311. The narrow beam may be sequentially changed (switched) as necessary. Further, the interval at which the processing procedure from step S306 to step S311 shown in FIG. 13 is repeated may be different from the interval at which the processing procedure from step S306 to step S311 is repeated.

Further, the mobile communication system according to the embodiment may transmit the format information together with the radio resource allocation information to the user apparatus 20 in the processing procedure of step S303 illustrated in FIG. In this case, the signal transmission unit 202 of the small base station 11 transmits, for example, the format information illustrated in FIG. 18A to the user device 20, and the signal transmission unit 102 of the user device 20 in the processing procedure of step S304. May transmit a reception quality report signal in the format shown in FIG. 18B, for example, to the small base station 11 in accordance with the format information notified in the processing procedure of step S303. Note that the format information shown in FIG. 18A may be the same as the format information shown in FIGS. 15A to 15D, for example.

Further, the user apparatus 20 and the small base station 11 may grasp in advance the configuration of the format information in FIG. The trouble of transmitting format information between the user apparatus 20 and the small base station 11 can be saved, and the amount of data transmitted and received between the user apparatus 20 and the small base station 11 can be reduced.

As another example, the mobile communication system according to the embodiment may transmit the format information together with the radio resource allocation information to the user apparatus 20 in the processing procedure of step S303 illustrated in FIG. In this case, the signal transmission unit 202 of the small base station 11 transmits, for example, the format information illustrated in FIG. 19A to the user device 20, and the signal transmission unit 102 of the user device 20 in the processing procedure of step S304. In accordance with the format information notified in the processing procedure of step S303, for example, a reception quality report signal in the format shown in FIG. 19B may be transmitted to the small base station 11. Note that the format information shown in FIG. 19A may be the same as the format information shown in FIG. 17A or 17B, for example.

Further, the user apparatus 20 and the small base station 11 may grasp in advance the configuration of the format information in FIG. The trouble of transmitting format information between the user apparatus 20 and the small base station 11 can be saved, and the amount of data transmitted and received between the user apparatus 20 and the small base station 11 can be reduced.

As yet another example, the mobile communication system according to the embodiment may transmit the format information together with the radio resource allocation information to the user apparatus 20 in the processing procedure of step S303 illustrated in FIG. In this case, the signal transmission unit 202 of the small base station 11 may transmit the format information illustrated in FIG. Further, in the processing procedure of step S304, the signal transmission unit 102 of the user apparatus 20 transmits a reception quality report signal in the format shown in FIG. 20B, for example, in accordance with the format information notified in the processing procedure of step S303. 11 may be transmitted. The format information shown in FIG. 20A stores, for example, “total number of beams”, and the format information included in FIG. 20B stores, for example, “number of beam sets”. It may be.

(Receiving quality report signal and feedback information transmission method)

FIG. 21 is a diagram for explaining a transmission method of a reception quality report signal and feedback information. A transmission method used when transmitting the reception quality report signal and the feedback information from the user apparatus 20 to the small base station 11 will be described with reference to FIG. First, FIG. 21A shows a state in which a reception quality report signal and feedback information are transmitted separately. As illustrated in FIG. 21A, the user apparatus 20 may transmit the reception quality report signal to the small base station 11 in a relatively long cycle compared to the feedback information.

Next, FIG. 21B shows a state in which the reception quality report signal and the feedback information are transmitted at the same time when the reception quality report signal is transmitted. As shown in FIG. 21 (b), the signal transmission unit 102 of the user apparatus 20 transmits the reception quality report signal including the feedback information to the small base station 11 at the timing when the reception quality report signal is transmitted. May be.

Here, an example of the format information format when the feedback information is included in the reception quality report signal will be described.

FIG. 22 is a diagram illustrating an example of format information to which a report pattern is assigned. In addition to the format information shown in FIGS. 15A to 15D, “report pattern” is given to the format information shown in FIG. The "report pattern" includes only the reception quality of the discovery signal corresponding to the narrow beam in the reception quality report signal, or includes both the reception quality of the discovery signal corresponding to the narrow beam and feedback information Information (flag) for identifying whether or not.

The information may be composed of 2 bits, for example, and may indicate four patterns. For example, when “00” is set in the “report pattern”, it may be indicated that the reception quality report signal includes only the reception quality of the discovery signal corresponding to the narrow beam. Similarly, when “01” is set, it may be indicated that the reception quality report signal includes both the reception quality of the discovery signal corresponding to the narrow beam and the feedback information.

Note that the format information shown in FIG. 22 may be used for reporting feedback information. For example, a flag (for example, “10”) indicating that only feedback information is included in the “report pattern” is added, and the format information shown in FIG. 22 is added to the header portion of the feedback information. It may be. In this case, zero may be stored in “number of beam sets”, “number of beams of beam set #N”, and “total number of beams” included in the format information. Thereby, the format of the signal transmitted from the user apparatus 20 to the small base station 11 is unified, and the processing load on the user apparatus 20 and the small base station 11 is reduced.

The configuration of the “report pattern” is an example, and other configurations may be used.

FIG. 23 is a diagram illustrating an example of a modification of the format information to which a report pattern is assigned. In addition to the format information shown in FIGS. 17A and 17B, “report pattern” is given to the format information shown in FIG. The information (flag) included in the “report pattern” is the same as that in FIG. Similarly to FIG. 22, the format information of FIG. 23 may be used for reporting feedback information.

(Discovery signal transmission method)

Next, a discovery signal transmission method corresponding to a narrow beam transmitted by the signal transmission unit 202 of the small base station 11 will be described.

FIG. 24 is a diagram illustrating an example of a discovery signal transmission method corresponding to a narrow beam. 24A to 24D, the horizontal axis indicates time, and the vertical axis indicates frequency. In addition, “H” indicates horizontal polarization, and “V” indicates vertical polarization. Further, the same hatching indicates that the signals are discovery signals corresponding to the same narrow beam (that is, a narrow beam having the same beam ID). In FIG. 24, the transmission timing of each discovery signal is not particularly defined, but may be transmitted at a predetermined cycle, for example.

First, FIG. 24A will be described. As shown in FIG. 24A, the signal transmission unit 202 transmits discovery signals corresponding to the same narrow beam at each transmission timing, for example, by frequency hopping. Moreover, the user apparatus 20 transmits the reception quality with respect to a discovery signal to the small base station 11 for every transmission timing. In other words, in the example of FIG. 24A, the discovery signal transmission timing (step S301 in FIG. 13) and the reception quality report timing (step S304 in FIG. 13) between the small base station 11 and the user apparatus 20 in advance. ) With one-to-one correspondence.

Next, FIG. 24B will be described. As shown in FIG. 24B, the signal transmission unit 202 transmits discovery signals corresponding to the same narrow beam at each transmission timing so as to cause frequency hopping. In addition, the user apparatus 20 measures reception quality from discovery signals received at a plurality of timings and transmits the reception quality to the small base station 11.

Next, FIG. 24C will be described. As shown in FIG. 24C, the signal transmission unit 202 transmits discovery signals corresponding to the same narrow beam at the same frequency (subcarrier) without frequency hopping at each transmission timing. . In addition, the user apparatus 20 measures reception quality from discovery signals received at a plurality of timings and transmits the reception quality to the small base station 11.

Next, FIG. 24D will be described. As shown in FIG. 24 (d), the signal transmission unit 202 uses a discovery signal corresponding to the same narrow beam at each transmission timing, for example, a frequency by mirroring as used in PUSCH transmission in LTE. Send as if hopping. That is, discovery signals corresponding to the same narrow beam are transmitted at the same frequency (subcarrier) at a constant period. In addition, the user apparatus 20 measures reception quality from discovery signals received at a plurality of timings and transmits the reception quality to the small base station 11.

According to the methods shown in FIGS. 24B to 24D, the user terminal can measure the reception quality from the discovery signal received at a plurality of timings, thereby eliminating the influence of noise included in the discovery signal. The reception quality can be measured with high accuracy. In addition, according to the methods of FIGS. 24B and 24D, the discovery signal is frequency hopped, so that the user terminal can measure the reception quality with high accuracy while eliminating the influence of the frequency. . In addition, according to the methods of FIGS. 24A to 24D, since the discovery signal is transmitted with different polarizations (vertical polarization and horizontal polarization), the user terminal measures reception quality with high accuracy. be able to.

In the present embodiment, a narrow beam discovery signal may be transmitted by a method different from that shown in FIG.

<Effect>

As described above, in the present embodiment, a user apparatus that communicates with the base station in a wireless communication system including a base station and a user apparatus, and a plurality of first devices transmitted from the base station Among a plurality of directivity patterns generated by a first receiving means for receiving a reference signal and a specific antenna port receiving the plurality of first reference signals, or a plurality of antenna ports, Detecting means for detecting a specific directivity pattern from which the first reference signal is received, measuring means for measuring the received power of each of the plurality of first reference signals, and the plurality of first reference signals Transmitting means for transmitting each received power to the base station in a group for each of the specific antenna port or the specific directivity pattern from which the plurality of first reference signals are received. User equipment.

By this user apparatus 20, in a radio communication system having a base station and a user apparatus that perform beam forming, a plurality of beams used for communication are appropriately selected from among a plurality of beams formed by the base station. Is possible.

In addition, the user apparatus may transmit header information indicating the number of the plurality of first reference signals belonging to the group to the base station. By transmitting such header information to the small base station 11, the small base station 11 can distinguish a plurality of first reference signals according to directions received by the user apparatus 20.

The first transmission unit may transmit the reception power of each of the plurality of first reference signals satisfying a predetermined condition to the base station in the group. Thereby, it becomes possible to reduce the amount of data when the received power is reported from the user apparatus 20 to the small base station 11.

In addition, the user apparatus measures second reception means for receiving one or more second reference signals transmitted from the base station, reception quality of the one or more second reference signals, and receives the reception Generating means for generating feedback information based on quality, wherein the transmitting means transmits the received power of each of the plurality of first reference signals and the feedback information to the base station at the same time. Also good. Accordingly, the user apparatus 20 can collectively transmit the reception power of the discovery signal corresponding to the narrow beam and the feedback information to the small base station 11, and is transmitted and received between the user apparatus 20 and the small base station 11. It is possible to reduce the number of signals to be transmitted.

The first transmission means receives header information indicating the number of the plurality of first reference signals belonging to the group from the base station, and based on the received header information, the plurality of first reference signals The received power of each reference signal may be divided into the group and transmitted to the base station. Thereby, the small base station 11 can designate a signal format for causing the user apparatus 20 to report the reception power of each of the plurality of first reference signals.

Further, the first receiving means may receive the plurality of first reference signals frequency-hopped from the base station. In addition, the measuring unit calculates received power of each of the plurality of first reference signals to be transmitted to the base station by measuring received power of each of the plurality of first reference signals a plurality of times. You may do it. Thereby, the user apparatus 20 can measure received power with higher accuracy.

Further, in the present embodiment, a base station that communicates with the user apparatus in a wireless communication system including a base station and a user apparatus, and a first transmission unit that transmits a plurality of first reference signals; First receiving means for receiving received power of each of the plurality of first reference signals grouped into a plurality of groups from the user device; and the plurality of first groups grouped into the plurality of groups. Selection means for selecting an antenna port for transmitting the second reference signal based on the received power of each of the reference signals, and one or more second reference signals are transmitted from the antenna port selected by the selection means Second transmitting means, second receiving means for receiving feedback information based on the reception quality of each of the one or more second reference signals from the user apparatus, and the feedback Based on the click information, the base station and a control means for controlling the antenna port is provided.

The small base station 11 appropriately selects a plurality of beams used for communication among a plurality of beams formed by the base station in a wireless communication system having a base station performing beam forming and a user apparatus. It becomes possible.

Further, the “means” in the configuration of each apparatus described above may be replaced with “unit”, “circuit”, “device”, and the like.

<Supplement of embodiment>

Although the embodiments have been described, the disclosed invention is not limited to such embodiments, and those skilled in the art will understand various variations, modifications, alternatives, substitutions, and the like. Although specific numerical examples have been described in order to facilitate understanding of the invention, these numerical values are merely examples and any appropriate values may be used unless otherwise specified. The classification of items in the above description is not essential to the present invention, and the items described in two or more items may be used in combination as necessary, or the items described in one item may be used in different items. It may be applied to the matters described in (if not inconsistent). The boundaries between functional units or processing units in the functional block diagram do not necessarily correspond to physical component boundaries. The operations of a plurality of functional units may be physically performed by one component, or the operations of one functional unit may be physically performed by a plurality of components. For convenience of explanation, the user apparatus and the base station have been described using functional block diagrams, but such an apparatus may be realized in hardware, software, or a combination thereof. Software operated by a processor included in a user apparatus and software operated by a processor included in a base station according to the embodiment of the present invention are random access memory (RAM), flash memory, read-only memory (ROM), EPROM, and EEPROM. , A register, a hard disk (HDD), a removable disk, a CD-ROM, a database, a server, or any other suitable storage medium. The present invention is not limited to the above embodiments, and various modifications, modifications, alternatives, substitutions, and the like are included in the present invention without departing from the spirit of the present invention.

In each embodiment, the discovery signal is an example of a first reference signal. The measurement reference signal is an example of a second reference signal. The signal receiving unit 101 is an example of a first receiving unit and a second transmitting unit. The reception direction detection unit 111 is an example of a detection unit. The reception quality measurement unit 103 is an example of a measurement unit. The signal transmission unit 102 is an example of a first transmission unit and a second transmission unit. The format information is an example of header information. The signal receiving unit 201 is an example of a first receiving unit and a second receiving unit. The signal transmission unit 202 is an example of a first transmission unit and a second transmission unit. The beam candidate selection unit 203 is an example of a selection unit. The beam control unit 204 is an example of a control unit.

This patent application claims priority based on Japanese Patent Application No. 2015-052709 filed on March 16, 2015, the entire contents of Japanese Patent Application No. 2015-052709 are incorporated herein by reference. To do.

10 Macro base station

11 Small base station

12 Small base station

20 User equipment

101 Signal receiver

102 Signal transmitter

103 Reception quality measurement unit

104 Feedback information generator

111 Reception direction detector

201 Signal receiver

202 Signal transmitter

203 Beam candidate selection unit

204 Beam controller

301 RF module

302 BB processing module

303 UE control module

401 RF module

402 BB processing module

403 Device control module

404 Communication IF

Claims (10)

A user apparatus that communicates with the base station in a wireless communication system comprising a base station and a user apparatus,

First receiving means for receiving a plurality of first reference signals transmitted from the base station;

A specific antenna port from which the plurality of first reference signals are received or a specific direction from which a plurality of directivity patterns generated by the plurality of antenna ports are received. Detecting means for detecting sex patterns;

Measuring means for measuring received power of each of the plurality of first reference signals;

The received power of each of the plurality of first reference signals is divided into groups for each of the specific antenna port or the specific directivity pattern from which the plurality of first reference signals are received, and transmitted to the base station Sending means to

A user device.

The user apparatus according to claim 1, wherein the transmission unit transmits header information indicating the number of the plurality of first reference signals belonging to the group to the base station.

The user apparatus according to claim 1 or 2, wherein the transmission unit divides reception power of each of the plurality of first reference signals satisfying a predetermined condition into the group and transmits the received power to the base station.

Second receiving means for receiving one or more second reference signals transmitted from the base station;

Generating means for measuring reception quality of the one or more second reference signals and generating feedback information based on the reception quality;

Have

4. The user apparatus according to claim 1, wherein the transmission unit transmits the reception power of each of the plurality of first reference signals and the feedback information to the base station at the same time.

The transmission means receives header information indicating the number of the plurality of first reference signals belonging to the group from the base station, and based on the received header information, each of the plurality of first reference signals The user apparatus according to claim 1, wherein received power is divided into the groups and transmitted to the base station.

6. The user apparatus according to claim 1, wherein the first reception unit receives the plurality of first reference signals frequency-hopped from the base station. 7.

The measurement means calculates reception power of each of the plurality of first reference signals to be transmitted to the base station by measuring reception power of each of the plurality of first reference signals a plurality of times. Item 7. The user device according to any one of Items 1 to 6.

A base station that communicates with the user apparatus in a wireless communication system comprising a base station and a user apparatus,

First transmission means for transmitting a plurality of first reference signals;

First receiving means for receiving received power of each of the plurality of first reference signals grouped into a plurality of groups from the user device;

Selection means for selecting an antenna port for transmitting a second reference signal based on the received power of each of the plurality of first reference signals grouped into the plurality of groups;

Second transmission means for transmitting one or more second reference signals from the antenna port selected by the selection means;

Second receiving means for receiving feedback information based on reception quality of each of the one or more second reference signals from the user apparatus;

Control means for controlling the antenna port based on the feedback information;

Base station with

A communication method executed by a user apparatus that communicates with the base station in a wireless communication system including a base station and a user apparatus,

Receiving a plurality of first reference signals transmitted from the base station;

A specific antenna port from which the plurality of first reference signals are received or a specific direction from which a plurality of directivity patterns generated by the plurality of antenna ports are received. A detecting step for detecting sex patterns;

A measurement step of measuring received power of each of the plurality of first reference signals;

The received power of each of the plurality of first reference signals is divided into groups for each of the specific antenna port or the specific directivity pattern from which the plurality of first reference signals are received, and transmitted to the base station Sending step to

A communication method comprising:

A communication method performed by a base station that communicates with the user apparatus in a wireless communication system comprising a base station and a user apparatus,

A first transmission step of transmitting a plurality of first reference signals;

A first receiving step of receiving the received power of each of the plurality of first reference signals grouped into a plurality of groups from the user device;

A selection step of selecting an antenna port for transmitting a second reference signal based on the received power of each of the plurality of first reference signals grouped into the plurality of groups;

A second transmission step of transmitting one or more second reference signals from the antenna port selected in the selection step;

A second reception step of receiving feedback information based on reception quality of each of the one or more second reference signals from the user apparatus;

A control step of controlling the antenna port based on the feedback information;

A communication method comprising:

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